Method and a system for controlling a heating plant

ABSTRACT

A method for controlling a heating plant as well as a control system for such a plant. More specifically the invention relates to the control of a heating plant adapted for local heating of surfaces to avoid ice and snow on such surfaces, and in particular controlling street heating plant or point heating plants (for rails), provided with one or several heating elements; so that a low power consumption is obtained. The control system is provided with at least one remotely operated unit ( 4 ) adapted to be controlled in such a manner that consumed energy is controlled in dependence of meteorological data representing present and anticipated temperatures and amounts of precipitation. The plant may also include one main station or weather station ( 10 ) which is influenced both by signals transmitted at a time depending of anticipated meteorological conditions and signals stating detected temperature and humidity at the weather station itself, and at least one satellite station ( 7 ) controlled by remote control only, e.g., via a modem, and then by a signal ( 16 ) transmitted form the weather station ( 10 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

A method for controlling a heating plant adapted for local heating of asurface to avoid ice and snow on this surface, in such a manner that alow energy consumption is obtained. The invention also relates to acontrol system for such a heating plant.

The invention especially relates to controlling of a heating plant insuch a manner that surfaces provided with heating elements heated byenergy supplied from e.g. electrical energy sources or from a heatedfluid are considered. The invention is substantially, but notexclusively used for local heating of areas with traffic such as streetsor sidewalks or selected parts of such areas.

In the following specification a heating plant adapted to heat a part ofa street by means of electrical energy substantially will be described,however, this is only an example as the invention also relates to plantsheating other objects, such as points for traffic on tracks or rails andheating plants using other forms of energy than electricity, e.g.heating flows of fluids or combinations of such plants.

2. Description of the Background Art

Previously, many kinds of street heating plants are known adopted forthe melting of snow. The simplest plants are built as an electricheating loop provided below the surface where an area without snow andice is desired. Such a plant is, in its most simple embodiment, madewithout any control system as it is provided only with an “on”/“off”switch which may be operated manually, and then the plant is switched“on” during cold periods when it is desirable that snow and ice shallmelt and flow away, while the plant is switched “off” during warmerperiods or when there is no precipitation in the shape of snow.Accordingly such plants have to be supervised constantly by a personpresent on the site and is technical spoken without any real controlsystem.

The above mentioned simple and manually controlled plants willnecessarily result in high operating and energy costs, both as theyrequire constant monitoring and as the users sometimes will forget toswitch the plant “off” when required. Accordingly, automatic plants havebeen developed provided with different kinds of detectors controllingthe switching “on” and switching “off” operations. Here only one plantshould be mentioned, described in Norwegian patent application No.92.3375 filed by the same applicant, and here an automatic plant isshown using a temperature detector having two thermostats or relays, andalso a humidity detector in the surface of a street. This detector will,together with the relays and electronic circuits adapted therefore,supply energy to the heating element only when precipitation and asurface temperature below zero occurs simultaneously. Then the plantwill be switched “on” only when precipitation takes place in periodswith a temperature below zero and be switched “off” both when thetemperature rise above a predetermined lower threshold value and alsowhen no precipitation is detected (no humidity detected).

Even when plants of the latter type is considered the energy consumptionoften will be higher than required. This depends especially on twoconditions:

1) The ground or surface temperature ought to be maintained on a ratherhigh “preparedness level” during cold and dry periods. Otherwise thesurface would, without any kind of energy supply during such periods, beextremely cooled down, and if snow should start falling after such along lasting cold period it would take a very long time before thesurface is sufficiently heated from its extremely low temperature sothat melting of snow will start. Accordingly, long periods with slushwould occur in the areal. By means of empiric experiments it has beenfound that such a “preparedness heating” of the surface during longlasting cold periods in many places will represent the highest portionof the energy consumption of such plants; in the area of the capitalOslo in Norway about 80%.

2) The users of such plants will often adjust the stand-by temperatureupwards more than required to avoid that snow will build up in the firsttime of each new fall of snow. Such a “faulty setting” of the plant willgive unnecessarily high working costs.

Another disadvantage with plants comprising heat detectors in the groundis that such detectors easily may be damaged by heavy traffic loads andtherefore deactivated whereafter the control of the plant will bedelusive. With a control system according to the present invention itwill not be necessary to use temperature detectors to measure the earthtemperature. Although existing plants comprising a detector fordetecting the ground temperature may easily be re-designed to actaccording to the present invention, so that the thermostat for earthtemperature may be removed or deactivated as its coupling temperature isadjusted below the existing temperature level. (In addition one or morerelatively inexpensive components may be added to the circuit duringsuch a re-designing process, as closer explained below).

Practical examinations have shown that the power consumption of a streetheating plant may be reduced to less than the half by undertaking thecontrol process according to the present invention. The economicaladvantages of such a solution will of course depend of the power price,but normally the additional costs of such a plant will be so low thatthe plant costs according to the invention will be saved after a shortoperating period.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for optimalcontrol of a heating plant in such a manner that the power consumptionis as low as possible without giving long periods with snow, ice orslush on the site. The object also is to provide a control system whichdoes not imply the disadvantages mentioned above, but which to thecontrary results in a cost effective working of the heating plantwithout any local maintenance. The power consumption then may be reducedfrom approximately 400 kWh/m²/year to about 150 kWh/m²/year (an examplevalid for street heating plants in the Oslo-region in south Norway),without other changes than explained above.

In very cold regions having relatively small amounts of precipitationduring the cold periods, much of the power consumption has so far beenused to keep a high stand-by temperature to avoid troublesome amounts ofslush, which will be the result if the plant is not switched “on” beforea snowfall begins.

By using a method and a control system according to the below claims,these advantages may be obtained. As a principle it may be said that theinvention is based on good and correct forecasts relating to anticipatedtemperatures and anticipated precipitation amounts in form of snow. Withgood forecasts a plant may be switched “off” during long lasting coldperiods without precipitation, no matter how low the temperature is.Only when precipitation having the shape of snow has been included inthe weather forecast it is required to switch the plant “on” and then ata determined period before the fall of snow starts. This time period mayagain be a function of the temperature at the moment, as the plantshould be switched “on” well in time before the fall of snow starts,especially when the temperature is very low, to secure that a suitablestart temperature is obtained before the beginning of the snowfall. Ifthe temperature is close to 0° C. and has been at this level for a longperiod, the switching “on” of the plant may wait until the verybeginning of the snowfall. In such a manner the duration of the timeperiod from switching “on” of the plant until the snow begins to fall,may be determined dependent of the preceding temperature changes. Athermostat monitoring the earth temperature may then also be superfluousin the plant, which also will lead to reduction of the working costs.

All the above advantages and objects may be met by using a method or acontrol system according to the patent claims stated below.

BRIEF DESCRIPTION OF THE INVENTION

To get a better understanding of the invention it is referred to thespecification describing some embodiments below, and in these examplesthe invention is explained with reference to a street heating plant withelectrical power supply, and it is also referred to the accompanyingdrawings where:

FIG. 1 shows the control of one single local heat plant comprising aremote control unit, according to the present invention. The plant alsocomprises the required actuator circuits and interfaces,

FIG. 2 shows a weather station or a reference plant which, according tothe invention, is used as a weather station for several heating plantswithin a region with approximately equal weather conditions at allplants. The weather station is based on a control system according toFIG. 1, but is in addition, equipped to control a series of satellitestations having a simpler design,

FIG. 3 shows how the central included in FIG. 1 and in FIG. 2 may bebased on a previously known automatic control plant of the type“SNØOSTAT”, as it is combined with a remotely operated unit 4 built upfrom one single “on”/“off” switch shunted by a local humidity detector6, and

FIG. 4 shows how a simpler satellite station may be constructed.

DETAILED DESCRIPTION OF THE INVENTION

It should already be mentioned that the embodiments shown as examples inthe figures should not be considered as a limitation of the invention.Accordingly, these examples may be varied still further than statedhere, though within the scope of the patent claims below. Further itshould be mentioned that the described embodiments do not include allpractical details which may be used to realize the invention, as theembodiments primarily aims at giving a description of the principle ofthe invention. However, the same reference numerals are used on allfigures for similar units and elements undertaking the same function,even if the elements and units may have a somewhat differentrepresentation.

On the figures the following references are used:

1—A control exchange preferably built up as a computer such as apersonal computer, comprises the exchange for automatic transmittingpredetermined operating or activating signals 15, adapted for connectingthe heating elements 8 to a power source 11. The signals are transmittedvia modems 2 (or a similar transmitter/receiver) to the communicationexchange 3.

2—A modem or (transceiver) adapted for transmitting/- receiving of theactivating signals 15.

3—A communication exchange for transmitting/retransmitting of anactivating signal 15, possibly as a radio signal or a telecommunicationsignal, e.g. in a paging system for controlling a remote operated unit4.

4—A remote operated unit e.g. including a controllable switch or a valvecontrolled by means of a radio signal or a similar telecommunicationsignal via a telecommunication network or a similar equipment.

5—A central in a weather station or in a local heating plant. Thiscentral may be specifically produced for such use or it may be are-designed previously known control circuit (e.g. a SNØ0STAT), adaptedto receive activating signals 15 and also to transmit such signalsfurther to satellite stations 7, e.g. via a modem 2.

6—A humidity sensor arranged in the surface and used in weather station10 (not necessarily in the satellite station 7).

7—Satellite station, i.e. a remote heating plant controlled by a localremote control unit, e.g. a remotely operated switch 4 in each singlesatellite station.

8—The heating element arranged at or in the surface which are to bemaintained without snow or ice.

9—A local control system, used only for a local heating element 8.

10—An area control system also called a weather station, being used incommon for a local heating plant and for one or more satellite stations7 having their local heating plants, arranged in one single weatherregion.

Both 9 and 10 are above referred to as a control system. However, acomplete control system according to the invention comprises also acontrol exchange 1, the communication central 3 and the communicationpaths with their modems and interfaces. The only components previouslyknown are the quite local control plants comprising the units 5(somewhat modified), 6, 8 and 11. The remaining components (comprising aquite new or a previously known re-designed exchange 5) are the elementsin the new control system. These details are explained in more detail inthe description below.

FIG. 1 refers to a local control plant according to the presentinvention, combined with an existing automatic heating plant. Accordingto the invention an activating signal 15 may be transmitted from thecontrol central 1. The communication exchange 3 may e.g. be a publicexchange based on a paging plant, or any other exchange adapted totransmit the activating signal 15 to the heating elements 8 in questionvia a local control system 9 (e.g. a redesigned SNØOSTAT delivered byJan Grosch AS). The new control or monitoring element in this circuit isa remotely operating unit, e.g. being shaped as a remotely controllingunit 4 including a remotely operated switch (or valve if a heated fluidis used as a power source 11) and the required activators, contactorsand interfaces coupled thereto. When an electric street heating plant isconsidered, the remotely controlled unit 4 comprises a switch deliveringa control signal for switching “on” the power source 11 (e.g. theelectrical mains system) to the heating element 8 positioned within thestreet body, or in a different surface, at a suitable place. If the areais not a street area but rather a point for rails or tracks which has tobe kept free for snow and ice, the heating element 8 may be arrangedbelow or into the track element comprising the point. The remotelycontrol unit 4 comprising a switch or a valve, is arranged on a suitablelocation between the heating element(s) 8 and the power source 11, nomatter what kind of power source being used.

It should be pointed out that the switch in the remotely operating unit4 normally does not switch the power used for heating, but only is acontrol element acting on contactors or actuators which in turn operatesthe power transmitting switch or valve assumed to right on FIG. 3.

The very control of the remotely operating unit 4 may take place by awireless transmission of an activating signal 15 via suitabletransceivers 2 (or possibly via aerials 12, as assumed in FIG. 4). Thesignal transmission may also take place via electrical or fibre opticalcables, and may then in a manner known per se, be superimposed onvoltages in the regular electrical mains network. As transmitter andreceiver 2 may be built in numerous different ways, these units are notdescribed in detail below, but on the figures it is assumed that thetransmitting of the signals 15 takes place via cables. However, itshould be mentioned that the control central 1 in turn may be controlledby meteorological data transmitted from a monitoring or controllingcentral 1 which first of all converts the metrological data intosuitable activating signals 15 having correct timely course for suchuse.

During cold periods the control centre 1 will transmit an activatingsignal 15 to the communication exchange 3. This exchange will retransmitthis activating signal 15 further to the local control system 9, andthen to a remotely operated unit 4 therein, which then is operatedaccording to the value of the activating signal 15. Now the exchange 5within the control system 9 takes hand of several functions. First ofall the central monitors the humidity in the ground or on the surface bymeans of the humidity sensor(s) 6. During relatively mild periods thesevalues shall alone control the plant as the heating elements 8 will besupplied with power when humidity is present and the temperature at thesame time is below a predetermined value, e.g. 0° C. During coldperiods, e.g. when the temperature is below −2° C., while the humiditysensors 6 at the same time detect that the surface is quite dry, thepreviously known plant would be switched “on” to maintain a certainstand-by temperature in the ground. According to the present inventionthe heat will be switched “on” first when the meteorological data tellthat precipitation and a low temperature are anticipated in a relativelynear future. First then the exchange 5, controlled by the remote controlunit 4, will be set to transmit power from the source 11 to the heatingelement 8 so that the surface temperature will start rising.

FIG. 2 shows the control plant for a more sophisticated regional heatingplant according to the invention, and the same reference numerals asused above are used wherever found expedient. However, the plant is heredesigned in such a manner that the regional control system 10 is used asa reference plant, also referred to as a regional weather station 10.This “weather station” is provided with a further transmitter or a modem2 added to the equipment shown in FIG. 1, and the further transmittersends an activating signal 16 to satellite stations 7 having a simplerequipment. The function will then substantially be the same as in thesystem described above according to FIG. 1; but simultaneously with theenergy transmitted from the power source 11 to the heating element(s) 8in the local station the central 5 starts transmitting orre-transmitting the activating signal, referred to as 16, in thedirection backwards toward the communication exchange 3. And thecommunication exchange 3 retransmits these activating signal 16 to oneor more satellite stations 7, which may have a far simpler design, asexplained below with reference to FIG. 4.

The transmission of the activity signals 15,16 may take place via acommon or via different cables/channels.

FIG. 3 shows a possible design of the exchange 5 according to FIG. 1 andFIG. 2 more in detail. The exchange may be based on a SNØOSTAT from JanGrosch AS, e.g. comprising a temperature sensor and/or a humidity meter.The SNØOSTAT may be reconstructed by removing the relay II (assumed onthe FIG. 3 by broken connections) and include a remote control unit 4comprising a remote switch in such a manner that the humidity meter willbe shunted by the remote operated switch. This switch is operated by theactivating signal 15. By closing the remotely operated switch thehumidity sensor 6 will be overruled and the heating element 8 will beswitched “on” even when humidity is not present, and this situation willoccur as soon as a snowfall is predicted.

To describe the working of a plant according to the present inventiontwo different working conditions will be considered below:

1) Low Temperature in the Ground (E.G. t<−2° C.)

When meteorological forecasts tell that precipitation is anticipated thecontrol central 1 is programmed to transmit an activating signal 15 viamodem 2 to the communication exchange 3 at a certain moment. This momentis preferably determined both by forecasts of expected precipitation andby the temperature during the last hours before such a forecast wasstated. To understand the principle for determining this switchingmoment, it may be mentioned that if there have been a strong cold periodfor a while and snowfall is anticipated, the heating has to be switched“on” well before the precipitation falls, so that the ground will beheated from the temperature in the surroundings to an acceptable standbytemperature before the snow begins to fall. Then it will be a shortperiod only, or may be no period at all, with slush in the area At thesame time the effect is that power is not used unnecessarily to heat thesurface during long periods without precipitation.

The activating signal 15 causes that the heat of the plant is switched“on”, and this signal may consist of a wireless signal or may betransmitted via cable, e.g. via a telephone network or via the ordinarymains network and then superimposed on the prevailing alternatingcurrent. The signal may be transmitted to the weather station 10 adaptedto control a switch connected in parallel to the humidity sensor 6 inthe exchange 5 by means of a remotely operated unit 4. In this mannerthe shunted humidity sensor will affect the automatic circuit in such amanner that the heat will be switched “on” as the circuit is made tobelieve that the precipitation already has started.

The power may be switched “off” in the following manner:

A while after the point of time at which the snowfall should havestarted, e.g. some hours thereafter, a new activating signal 15 (orpassivating signal) is transmitted from the control central 1 via themodem 2 to the communication exchange 3 and retransmitted to theremotely controlled unit 4 provided with a remotely operated switch, todecouple the short circuiting over the input terminal of the humiditysensor 6, so that this sensor does not any longer indicate humidity ifnot real humidity exists on the sensor.

If the sensor is dry or when it becomes dry, the exchange 5 willtransmit a signal 16 to switch “off” the heat in satellite station 7.This signal is transmitted via the modem 2 and also via thetelecommunication network and finally via the communication exchange 3.In this working condition the meteorological anticipations ofprecipitation and cold weather will result in switching “on” the heatingplant, while this heating will :be turned “off” after a certainpredetermined time if the precipitation did not some or has ceased.

2) A High Surface Temperature (E. G. −2° C. <t>0° C.)

During periods with precipitation the exchange 5 in the weather station10 will give a signal which will switch “on” the heating element 8. Asignal is also transmitted to the modem 2 and via the telecommunicationnetwork to a communication exchange 3. The communication exchange 3 thenwill transmit a start signal to the satellite station(s) 7.

When the humidity detector 6 is dry the central 5 transmits a signal toswitch “off” the heating element 8. This signal will also be sent to themodem 2 and via the telecommunication network the signal is beingtransmitted to the communication exchange 3 which then transmits adis-connecting signal to the satellites 7. In this condition then thedetector 6 in the weather station 10 will itself both start and stop theheating process.

If desired each single satellite station 7 may be controlled manuallyfrom the control central 1.

FIG. 4 shows the design of a very simple satellite station 7. Here thecontrol is assumed to take place by a wireless transmission of signalsto the aerial 12. The signals are received and treated in the remotelyoperated unit 4 which operates a remotely operated switch therein, andconnects or disconnects the power source 11 to/from the heating element8. The activating signal 16 is normally transmitted from the weatherstation 7 via its modem 2, but may also be transmitted directly from thecontrol central 1. It should be mentioned that the heating plant may useany kind of inexpensive and accessible energy within the region. InNorway it is suitable to use electrical energy as water energy plantsgives inexpensive electricity. The remotely operated unit 4 may theninclude an electric or electronic switch, or any kind of regulatorpreviously known. In other countries and in other epochs other kinds ofpower may be used. Plants where the energy is supplied as a heated fluidmay e.g. be assumed, and then the controllable element may be designedas a valve of “on”/“off” type or an adjust and remotely operated valvethrough which the fluid passes.

The new control system may be combined with different kinds ofpreviously known control plants. Although the embodiments above refersto a combination of a remotely operated unit and a SNØOSTAT-unit fromthe above mentioned Norwegian firm, this does not exclude combination ofthe invention with other automatic plants.

Although the remotely operating process referred to in the embodimentscomprises a remotely operated switch, this does not exclude use of amore sophisticated remotely operated element than such an “on”/“off”element. The remotely operated unit may e.g. include a stepwiseregulating device, e.g. a previously known varistor or thyristorconnection, often used as a dimmer for light sources, in which thesupplied energy is electrical AC energy, and where the power output isvaried by varying the circuit's duty cycle, or the output may include astep motor which in turn regulates a valve.

The very signal used for the remotely operating process will normally bea radio signal and this signal may be coded or predetermined in such amanner that only the desired receivers within reach of the signals willreact.

The economical reason for such a control system may be that theincreased building costs will be saved within short due to stronglyreduced operating costs. In these days with a shortage of energy,economic use of the resources without pollution is important. In acountry as Norway it should therefore not be underestimated that usingsuch power saving plants may delay or make new, expensive erection ofnew power stations unnecessary.

It should also be mentioned that the invention may be used in such a waythat the service itself, to switch a plant “on” and “off” at optimaltime intervals, is the primary thing to be marketed. The result is thatthe operation will be both economic and advantageous as street heatingplants will avoid long periods with slush on the heated area. Theinvention may also be used on existing plants as the equipment simplymay be re-designed to obtain remotely operation. For existing plants ofthe type SNØOSTAT, the only change may be to set the thermostatmeasuring the ground temperature at so low a level that the thermostatwill not be activated, and in addition a remotely operated switch may beadded in the circuit in such a manner that the humidity meter will beshunted by the switch. Accordingly, the operation of the remotelyoperated switch will, by the circuit, be interpreted as if the ground ishumid, and as a result the heating element(s) will be switched “on”.

The object is to provide a control plant giving a shorter period withslush and saving considerably amounts of power during use, and also tooffer services for controlling heating plants in such a manner thatsavings and advantageous operation is obtained.

While a preferred embodiment of the present invention has been describedabove, it should be understood that it has been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by the above described exemplaryembodiment.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that the invention may be practiced otherwise than asspecifically described herein.

What is claimed is:
 1. A control system for at least one heating plantprovided with heating element (8) and adapted for heating of one orseveral surfaces by power supply from a power source (11) for avoidingice and snow generation on the surface(s), at a low power consumption,characterized in that the control system comprises: a control central(1) adapted to obtain regional meteorological data and to transmit apredetermined activating signal (15) for activating the heating elementvia an existing communication network (2, 3) at a point of timedepending on said data, a local control system (9,10) adapted to receivean activating signal (15) and provided with at least one remotelycontrolled unit (4) adapted to be effected by the activating signal(15); so that power supplied from a power source (11) to the heatingelement(s) (8) is changed dependent of the regional meteorological data.2. A control system for a heating plant as stated in claim 1,characterized in that the control system (9,10) comprises an exchange(5) adapted to react on locally detected temperature and humidityvalues, detected by at least one local detector (6), and also to reacton the received activating signal(s) (15).
 3. A control system for aheating plant as stated in claim 1, and where the energy is supplied aselectrical energy, characterized in that said remotely operated elementcomprises a controllable contractor (e.g. a thyristor or varistorcontrolled contractor) being able to supply the street surface with avariable amount of energy by varying the duty cycle of the workingcurrent.
 4. A control system for at least one heating plant providedwith heating element (8) and adapted for heating of one or severalsurfaces by power supply from a power source (11) for avoiding ice andsnow generation on the surface(s), at a low power consumption,characterized in that the control system comprises: a control central(1) adapted to obtain regional meteorological data and to transmit apredetermined activating signal (15) for activating the heating elementvia an existing communication network (2, 3) at a point of timedepending on said data, a regional control system (9, 10) adapted toreceive an activating signal (15) and provided with at least oneremotely controlled unit (4) adapted to be effected by the activatingsignal (15); so that power supplied from a power source (11) to theheating element(s) (8) is changed dependent on the regionalmeteorological data.
 5. A control system for at least one heating plantprovided with heating element (8) and adapted for heating of one orseveral surfaces by power supply from a power source (11) for avoidingice and snow generation on the surface(s), at a low power consumption,characterized in that the control system comprises: a control central(1) adapted to obtain regional meteorological data and to transmit apredetermined activating signal (15) for activating the heating elementvia an existing communication network (2, 3) at a point of timedepending on said data, a local/regional control system (9, 10) adaptedto receive an activating signal (15) and provided with at least oneremotely controlled unit (4) adapted to be effected by the activatingsignal (15); so that power supplied from a power source (11) to theheating element(s) (8) is changed dependent on the regionalmeteorological data, and an exchange (5) arranged as part of thelocal/regional control system and adapted to react on locally detectedtemperature and humidity values, detected by at least one local detector(6), and also to react on the received activating signal(s) (15).
 6. Amethod for controlling a heating plant comprising at least one heatingelement (8) adapted for locally heating of a surface, at a low powerconsumption, to avoid ice or snow on the surface, characterized in thatregional meteorological data are obtained, in particular related toregional temperature progress and anticipated regional precipitation, anactivating signal (15) is transmitted at a point of time deduced frommeteorological data, said activating signal (15) is further transmittedto at least one remotely operated unit (4) connected to the heatingelement(s) (8) and is operating these elements, and that the point oftime for transmitting the activating signal (15,16) is determined insuch a manner that the heating element(s) (8) is/are passivated duringcold periods without precipitation, but all the same is/are activated ata certain adjustable point of time succeeding the point of time whenprecipitation is anticipated according to the regional meteorologicaldata.
 7. A method as stated in claim 6, characterized in that at leastone of the heating elements (8) within the region also is/are controlledby at least one locally arranged humidity and/or temperature detector(6) registrating local humidity and/or local temperature close to theheating element(s) (8).
 8. A method as stated in claim 7, used with aheating plant comprising several heating elements (8) distributed overone geographic region having substantially the equal meteorologicalconditions, characterized in that a reference plant (10) controlling atleast one heating element (8) is selected as the only plant receivingthe activating signal (15) directly and also being controlled by thissignal within this region, while at least one different heating plant(7) within the same region is/are controlled by further remotelycontrolling signals (16) generated in or retransmitted from saidreference plant (10).
 9. A control system as stated in claim 8,characterized in that the system comprises several controllable heatingelements (8) distributed over several separated heating plantsdistributed over a region with substantially equal weather conditions,that one of the heating plants within a region represents a regionalweather station (10) acting as a reference plant and provided with amodem (14) adapted for transmitting a remotely operating signal (1) tothe remaining satellite plants (7) within the region, while eachsatellite station (7) comprises a heating plant controlled only by anactivating signal (16) from the regional weather station (10).
 10. Amethod as claimed in claim 6, characterized in that the exact point oftime for transmitting the activating signal (15) and therebyactivating/passivating the heating element(s) (8), is adjusted independence of the regional temperature progress.
 11. A method as statedin claim 6, characterized in that the activating signals (15) are basedon information delivered by the public meteorological forecast services.